Add WebGL visual regression tests for transform functions

[aashu2006]

Resolves #8464

Changes:

• Added a new Transforms visual test suite for WebGL
• Added visual regression tests for:
  • translate() moving shapes along x and y axes
  • rotate() rotating shapes around the z-axis
  • scale() uniformly scaling shapes
• Added baseline screenshots for the new visual tests

Scope is limited to visual tests only; no rendering or engine code changes.

Screenshots of the change:
Baseline screenshots for the new visual tests are included in
test/unit/visual/screenshots/WebGL/Transforms/.

PR Checklist

• npm run lint passes
• [Inline reference] is included / updated
• [Unit tests] are included / updated